Three design phases occur typically before a new electronic circuit design is released for high-volume manufacture. The first phase is the design of the circuit, which is typically performed using computer-aided design (CAD). CAD is computer software that models the circuit generating its theoretical performance.
The second phase is testing the CAD model with a prototype circuit. A prototype circuit is a hand-wired assembly with physical electronic components. The advantages of building and testing a prototype circuit are multifold. The first is it validates the final selection of the electronic components. Often a component's cost, lead-time, or pending obsolesce, forces the designer to substitute the theoretical CAD values with the closest parts commercially available. A prototype circuit ensures these alternate components do not adversely affect the final circuit performance. Secondly, it tests design parameters historically difficult to model in CAD, such as grounding issues, electrical noise, or thermal effects. Finally, and often most importantly, a prototype circuit interfaces and operates real-world devices: a feature impossible with CAD software.
The final (third) design phase is a low-volume fabrication of the circuit in final production form. Typically this includes mounting all the components onto a custom designed printed circuit board (PCB); this phase is commonly referred to in the industry as a ‘first article’ PCB. The first article PCB is then extensively tested before the design is approved to high-volume production.
Although these three phases have been followed for decades, problems still exist within this design paradigm. While advances in CAD software have dramatically reduced the initial circuit design phase, unfortunately, no similar advances have paralleled for circuit prototyping technology. Using current prototyping technology, the time required to assemble even a relatively simple circuit, i.e. with only a dozen electronic components, can take days of intense labor. Larger designs, with 50 or more components, may require weeks.
Circuit designers with impacted schedules are often forced to skip the prototyping phase altogether; proceeding directly from the CAD model to a first article PCB. This path appears, at least initially, to shorten the design cycle, but entails a significant amount of risk. The reason is the cost to produce a first article PCB is significant, in both time and money, and investing this on a design only theoretically modeled in CAD can result in a PCB with a multitude of design errors. This issue is further complicated due to the fact that design errors on the finished PCB are now extremely difficult, or impossible, to correct. The problem is every electrical component soldered to a PCB requires a matching solder pattern, or ‘footprint’, as known in the industry. If a PCB design error requires a new component, employing an alternate footprint, it can't be soldered to the PCB. Even if the footprints match, the new component's pin-for-pin functionality, also known as its ‘pin compatibility’, may differ resulting in circuit incompatibility. If either of these conditions exists, the PCB cannot be easily modified, and often must be scrapped and redesigned again incurring further cost and project delays.
The circuit designer today, therefore, must choose between the time and labor to prototype a circuit to validate its performance vs. the cost of producing, often a series, of un-modifiable PCBs. It would be a significant advantage to the circuit designer to have a method available that facilitates both rapid circuit prototyping plus has the additional ability to easily modify PCB solder footprints to correct design errors.
Many types of circuit prototyping methods and technologies currently exist, but all have limitations or inherent drawbacks to their designs. In addition, none of these existing prototype methods have useful applications to easily modify a PCB's component's solder footprints.
The prototype method selected by the designer depends primarily upon the size of the circuit, i.e. the number of electronic components, and their technology. Two primary component types exist today; through-hole and surface mount technology (SMT). As their names imply, through-hole electrical components are soldered into hole patterns on a PCB while SMT devices are soldered only to the surface.
One of the earliest types of through-hole prototyping technologies employ electrically conductive sockets into which the through-hole component's leads are inserted without solder. Several problems, however, exist with all socket prototype methods. The first is the prototype circuits developed inherently lack a continuous, power or ground plane, so the circuit's power and clock speeds are limited. Second, socket connection methods have a long history in the industry for generating intermittent electrical connections, especially after age and repeated use. Due to these limitations, socket prototype methods are normally only employed by hobbyist or used in classroom experimentation. Attempting to use these socket prototype technologies to modify a PCB's solder footprints is virtually impossible.
An alternate prototype method employs a PCB fabricated with a variety of solder footprints onto which the designer solders the electronic components and wires. This method is known in the industry as a proto-PCB and may be used for through-hole or SMT devices. Proto-PCB methods have several advantages over socket prototype methods, since soldering the components and wires directly to the proto-PCB significantly improve the electrical connections and mechanical robustness. Also, the internal power and ground planes provided within the proto-PCB enable higher power and faster circuit clock speeds.
The inherent limitation, however, with any proto-PCB method is the finite number of solder footprints available, limiting the component types and circuit size. In addition, repeated soldering and de-soldering components, typically performed in a prototype development phase, can result in permanent damage the proto-PCB's solder footprints. If a critical number of these solder footprints were damaged, the entire circuit must be scrapped and reassembled again on a new proto-PCB. Like other single, monolithic assemblies previously described, proto-PCB boards are too large to be effectively mounted to a PCB, and as such can not be used as a method to modify individual solder footprints on a PCB.
In the 1990's, the electronics industry began phasing out through-hole devices in favor of SMT components, and today SMT devices are employed almost exclusively in all new PCB designs. SMT components are soldered only to the surface of a PCB and, therefore, can be designed much smaller than their through-hole counterparts. A typical SMT integrated component (IC), can have a body size less than 12 mm long with electrical leads less than 0.5 mm long. Prototyping a circuit by hand soldering wires directly to a 0.5 mm SMT component lead is virtually impossible, even under a microscope. For this reason, all SMT prototype methods require the SMT component to be first soldered to a small interface PCB, or ‘component adapter’ as commonly known in the industry. Each component adapter typically has a single solder footprint and employ traces connecting the component's leads to larger solder patterns. The larger solder patterns enable the user to hand-solder wires relatively easily. Component adapters have advantages over monolithic proto-board methods, since an unlimited number of component adapters can be incorporated generating prototype circuits of any size, and individual adapters may be added or replaced if damaged without affecting the entire circuit.
One drawback, however, with all component adapter methods is their small size: a design requirement necessary to reduce the overall size of the prototype circuit. A typical component adapter is not much larger than its single solder footprint and often less than 25 mm×25 mm in size. Soldering components and wires to a multitude of these small component adapters are often so difficult any attempt at a logical design layout is usually abandoned. In the end most prototype component adapter circuits resemble, and are commonly referred to in the industry, as a ‘rats nest’ of wires. Once assembled, modifications to such a circuit are definitely not for the faint hearted. A second limitation is the prototype circuits formed by these individual adapters lack any type of continuous power or ground plane thus the circuit's clock speeds and performance are limited. Finally, nothing is provided in any of these methods to fixture the individual component adapters either to a surface, or each other. The final assembly is very mechanically fragile and often can't be transported, restricting them to static applications such as an engineering bench.
With simply nothing else available to the designer today, these component adapters are often forced into service as a method to correct PCB design errors, but with limited results. One problem is the adapters are designed from rigid materials, so it's time-consuming to cut and shape them to fit the irregular spaces of a PCB. Secondly, due to the risk of electrical shorts, the component adapters normally can't be placed on, or near, exposed PCB traces. The result is adapters being mounted relatively far from their intended location requiring lengthy, exposed wiring reducing circuit performance and increasing electrical noise. Lastly, none of the component adapters available today provide a method to fixture the component adapters either to a surface, or each other, so it's left to the designer to glue, tape, or screw etc. the adapters to the PCB. This extra step adds further time to an already time-consuming process and, depending on the method, can result in permanent damage to the PCB.
An alternate type of component adapter as suggested by U.S. Pat. No. 6,265,952 (Kan, 2001) includes a method in which the component adapters are designed with permanent leads matching hole patterns of a passive hole matrix proto-board. This feature allows the component adapters to be mounted securely to the holes of the proto-board improving mechanical strength and organization. The adapter's leads also provide an easy connection point for the prototype circuit's wires for hand soldering or wire wrapping. The design trade-off, however, for having permanent leads is it limits the adapters to single-use applications, since a hole matrix proto-board, or similar, is required to mount the adapter. As such, this component adapter design cannot develop circuits with continuous power or ground planes, which again limits the clock speeds and performance of the prototype circuit. The second drawback is the fixed leads prevent the adapters for use as a method to modify PCB footprints. All through-hole type adapters require matching hole patterns, so these device can't modify a PCB component's solder footprint or its pin compatibility.
A similar type of hole matrix proto-board mounted component adapter is suggested by U.S. Pat. No. 4,871,317 (Jones, 1989). In this adaptation, the component adapters are formed using flexible vs. rigid PCB technology and attachable leads vs. the permanent leads as described in U.S. Pat. No. 6,265,952 (Kan, 2001). The major drawback to this design, however, is the designer must solder a separate wire-wrap pin array to each component adapter in order mount the component adapters to a hole matrix proto-board. Although this concept would work, it significantly increases the assembly time compared to other prototype methods currently available. Even with the pin adapters soldered, the prototype circuit developed is still a wire-wrapped assembly. Wire wrap prototype circuits are prone to intermittent electrical connections and inherently lack continuous power or ground planes limiting the circuit's power and clock speeds.
Other embodiments of the component adapters suggested by U.S. Pat. No. 4,871,317 (Jones, 1989) do not include wire-wrap pins soldered to the adapters. However, this configuration is even further problematic. Without the wire-wrap pin arrays, the component adapters can't be aligned to the proto-board holes, therefore, the designer needs to hand-align the component adapters to the proto-board holes, while simultaneously attempting to solder the interconnecting wires: a time consuming and difficult process. Furthermore, nothing is provided in this mode to fixture the component adapters, either to the proto-board or each other. As a result, prototype circuits developed in this adaptation are more mechanically fragile than rigid component adapters due to the thin flexible materials employed. In this scenario it can be seen the function and inherent drawbacks are now identical, or in some cases worse, to other component adapters described above.
In summary, therefore, all previous electronic circuit prototype methods have the following disadvantages or design trade-offs:                (a) Are time consuming and difficult to assemble.        (b) Result in prototype circuits that are mechanically fragile.        (c) Result in prototype circuits that are unorganized.        (d) Limit the prototype circuit in size or component types.        (e) Require component adapters with external pins or other mounting hardware.        (f) Employ component adapters restricted to hole-matrix or proto-board applications.        (g) Develop prototype circuits that are difficult to modify or repair.        (h) Cannot develop prototype circuits with power or ground planes.        (i) Develop prototype circuits with intermittent electrical connections.        (j) Are all restricted to single-use applications and are an ineffective method to modify the solder footprints of a PCB circuit.        
It is desirable to have a method, system and apparatus for addressing the above-listed problems of electronic circuit prototyping.